Re: Web Rule Language - WRL vs SWRL

---- Original message ----
>Date: Wed, 22 Jun 2005 10:46:36 -0400
>From: Jim Hendler <hendler@cs.umd.edu>  
>Subject: Re: Web Rule Language - WRL vs SWRL  
>To: Jos de Bruijn <jos.debruijn@deri.org>, dreer@fh-furtwangen.de
>Cc: public-sws-ig@w3.org
[snip]
>Sorry, but this cannot be right.  SWRL assumes closed world semantics 
>and WRL assumes open world semantics.   

Thinko/typo on Jim's part. It's the other way around of course.

> Thus, we get completely 
>different entailments in an OWL/RDF world than in a WRL one, so we 
>are talking something very different than a subset relationship.  Ian 
>Horrocks, Peter Patel-Schneider, and Bijan Parsia (with me as a 
>kibbitzer) wrote a short paper about this available at [1]
>
>Let me be clear, I'm all for Web (and Sem Web) rules languages, but 
>if it isn't open-world, I don't see how it can be Sem Web, since it 
>violates the base assumption on which all of RDF, RDFS, and OWL sit. 
>This is easily fixable, and at the Rules workshop the idea of a 
>"Scoped Negation as Failure" was developed to handle this -- I'd love 
>to see WRL (and SWRL) extended to have a SNAF mechanism, because then 
>we don't violate the basic principles of the Web architecture and the 
>Semantic Web, but we should be precise - two things with very 
>different Semantics and entailments cannot be referred to as subsets 
>of each other.
[snip]

To extend the conversation in another direction, is there any reason to think 
that a logic programming paradigm, in general, is the right approach to nonmon 
on the Web? Representationally? There are many non-monontonic formalisms 
(consider default logic and autoepistemic logic) and it might be that they 1) are 
better for web contexts and 2) play better with owl. (It's plausible, for example, 
to think that default logic can be made to fit better because of the separatation 
of the base representation and the default rules. Even there, adjustements must 
be made.)

(Of course, anything in this space runs into the problem that, in general, 
nonmon formalism are much more computationally difficult than corresponding 
monotonic ones. The LP position often appeals to the scalablility/computational 
goodness of, say, deductive databases. But if that comes at the price of 
throttling back expressivity forever...maybe it's not such a great idea. Pat Hayes 
often, to my understand this, as thinking of nonmon constructs as part of the 
*data* on the web (to his mind, bad), and nonmon as a way of *reasoning with* 
the data on the web (good...it's located in the agent or processor which is in a 
position to make certain assumptions with a good sense of the risks)).

Cheers,
Bijan Parsia.

Received on Wednesday, 22 June 2005 14:59:51 UTC